Defect-Guided Assembly of Aperiodic and Flexible Metal-Organic Frameworks From Pre-Formed Cages.

Controlling the spatial distribution of defects in metal-organic frameworks (MOFs) remains a fundamental challenge in defect engineering. Here, we report a cage-directed assembly strategy that enables the programmed introduction of topologically correlated defects and induces aperiodicity in HKUST-1-type frameworks. Pre-synthesised Rh(II) metal-organic cages or polyhedra (MOPs) act as persistent cavities that template the formation of HKUST-1-based networks containing linker-induced Cu-vacancy domains confined within discrete cuboctahedral cavities. The use of dicarboxylate linkers, in which one carboxylate group is missing compared to the original 1,3,5-benzenetricarboxylate linker, gives rise to nine distinct local defect configurations that are independently distributed throughout the lattice. This results in an aperiodic framework with preserved long-range crystallinity. The resulting materials exhibit hierarchical micro-mesoporosity, reversible loss and recovery of crystallinity, and a pronounced solvent-induced breathing response. This work demonstrates that combining pre-formed cages with linkers with reduced connectivity can be a new strategy to localise defects and access aperiodic MOFs with emergent structural adaptability.